Clouds and Visibility at Flight Level

METEOROLOGY FLIGHT PLANNING

CHAPTER FOUR

Figure 4-4 Part II: En Route Data Section

Blocks 14 and 15: Flight Level Winds/Temperature

This block is filled in with data from the Winds-Aloft Forecasts (FDs) and Winds-Aloft

Prognostic Charts. However, forecasters will generally not choose a flight altitude for you; that

is your decision to make before handing in the DD 175 to METRO. Thus, the sources used to fill

in the following blocks should be given an overview by the aircrew before the flight weather

brief in order to select a flight altitude, as will be discussed in the next section, Selection of a

Flight Level.

Blocks 16 and 17: Clouds and Visibility at Flight Level

Clouds at flight level and minimum visibility at flight level will generally be apparent from the

overall weather picture provided during the weather briefing. This information may be

supplemented with Pilot Weather Reports, which are also useful in obtaining other information

not readily accessible in other specific charts and reports. These are available in Teletype format

under the heading "UA."

Notice there are three boxes within Block 16 that may be checked. A check in the "YES" box

represents a forecast for greater than 45% of the time spent in clouds at the flight level in Block

14. A check in the "NO" box indicates less than 1% of the time will be spent in clouds, while a

check in the "IN AND OUT" box indicates between 1% and 45% of the flight will be through

clouds. If it is more practical to check more than one block to better represent cloud conditions,

then the corresponding locations will be entered above the additional blocks.

FLIGHT WEATHER BRIEFING FORM, DD FORM 175-1 4-7